Concrete — anchorage length and reinforcement laps
Design anchorage length and design lap length of reinforcing bars in tension and compression to clauses 8.4 and 8.7 of EN 1992-1-1 including the Czech National Annex.
Calculation mode
Materials
fck = 25 MPa · fctk,0.05 = 1.8 MPa · fyk = 500 MPa
Bar and anchorage
The bend, hook and loop options apply only to a standard shape to Figure 8.1 of EC2: a bend with 90° ≤ α < 150° or a hook with α ≥ 150°, with a straight part of at least 5φ beyond the bend, or a loop; mandrel diameter at least to Table 8.1N. The calculator does not check the shape geometry or concrete failure inside the bend (clause 8.3).
Bends and hooks do not contribute to compression anchorages (clause 8.4.1(3)).
Good: members with h ≤ 250 mm; bars inclined at 45°–90° to the horizontal; for h > 250 mm bars in the bottom 250 mm; for h > 600 mm bars more than 300 mm below the top surface.
Other: all remaining cases and members cast with slip-forms, unless shown otherwise.
Cover and bar spacing
In compression the effect of the cover is not taken into account (α1 = α2 = 1.0).
Actual cover to the anchored bar (usually cnom).
If the bar is not at a side face of the member, enter the distance to the nearest side face.
If there is no other anchored bar next to the anchored bar, enter a distance for which a/2 does not govern.
Further parameters
Show advanced settings
Stress at the position from where the anchorage is measured (clause 8.4.3(2)); at most fyd. Used for both lb,rqd and lb,min.
Only non-welded transverse reinforcement within lbd; a welded bar taken into account in α4 does not belong here. The calculator does not verify that the reinforcement actually lies within lbd.
Conditions: a welded transverse bar of diameter φt > 0.6φ (clause 8.4.4(1)), position and arrangement to Figure 8.1e, proven quality of the welded joints (clause 8.6(1)).
The calculator does not verify the geometric or detailing conditions; by ticking the box you adopt them as an input assumption.
Transverse pressure perpendicular to the plane of splitting at the ultimate limit state; used in tension only.
αct = 1.0 (NA.2.13). Read only.
Materials
fck = 25 MPa · fctk,0.05 = 1.8 MPa · fyk = 500 MPa
Bars and lap
Straight bars of equal diameter lapped (clause 8.7.3), α1 = 1.0.
Good: members with h ≤ 250 mm; bars inclined at 45°–90° to the horizontal; for h > 250 mm bars in the bottom 250 mm; for h > 600 mm bars more than 300 mm below the top surface.
Other: all remaining cases and members cast with slip-forms, unless shown otherwise.
Percentage of reinforcement lapped within ±0.65·l0 of the centre of the lap considered (Figure 8.8). The default 100 % is on the safe side; enter a lower value only for verified staggering of the laps.
Clear distance between the two bars of one lap; 0 = the bars touch (clause 8.2(4)). If it exceeds min(4φ; 50 mm), the lap length is increased by the difference (clause 8.7.2(3)).
Cover and bar spacing
In compression the effect of the cover is not taken into account (α2 = 1.0); the distance a is used only to check the arrangement to clause 8.7.2(3).
Actual cover to the lapped bars (usually cnom).
If the bar is not at a side face of the member, enter the distance to the nearest side face.
Clear distance between adjacent laps (Figure 8.7). In tension it enters cd = min(a/2; c1; c); in tension and compression it is compared with max(2φ; 20 mm). If in doubt, enter the smaller value.
Further parameters
Show advanced settings
Design stress in the lapped bars at the lap (clause 8.4.3(2)); at most fyd. Used for lb,rqd, l0,min and ΣAst,min in α3.
Only non-welded transverse reinforcement within the lap length l0. The calculator does not verify that the reinforcement actually lies within l0.
Transverse pressure perpendicular to the plane of splitting at the ultimate limit state; used in tension only.
αct = 1.0 (NA.2.13). Read only.
- The Anchorage length mode determines the design anchorage length of one ribbed reinforcing bar to clause 8.4 of EN 1992-1-1 and the Czech National Annex. Plain bars, prestressing steel and mechanical anchorage devices are not covered.
- Coefficients α1 to α5 are determined from Table 8.2. The favourable effect of transverse reinforcement, a welded transverse bar and transverse pressure is used only if you explicitly enter it; the calculator does not verify the conditions for using them.
- The bend, hook and loop options assume a standard shape to Figure 8.1; the anchorage length is then measured along the centreline of the bar. The calculator does not check the shape geometry, the mandrel diameter or concrete failure inside the bend to clause 8.3.
- The Reinforcement laps mode determines the design lap length l0 of straight bars of equal diameter to clause 8.7.3; the coefficient α6 = √(ρ1/25) follows from the entered proportion of lapped bars. The calculator does not check the arrangement of laps, the transverse reinforcement or the rules for large diameters — it lists them as detailing requirements.
- The calculator does not cover laps of bundled bars and of welded fabric, mechanical couplers, anchorage of bundled bars and of fabric with pairs of wires, anchorage of links, or the special rules for anchorage at supports.
- This is not a substitute for a complete structural design.